Sintered alloy for valve seat

Abstract

A sintered alloy for a valve seat comprising, in weight percent, 0.5 to 1.7% C, 0.5 to 2.5% Ni, 3.0 to 8.0% Cr, 0.1 to 0.9% Mo, 1.0 to 3.8% W and 4.5 to 8.5% Co, the balance being substantially Fe provided by a base atomized powder; said alloy containing 8 to 14% by volume of 250 mesh or less C-Cr-W-Co-Fe and Fe-Mo hard grains and 6 to 13% by volume of cells, with the continuous cells being infiltrated by a copper alloy.

We claim: 
     
       1. A sintered alloy material for valve seats, in which hard grains are dispersed in a base structure and sintering cells are infiltrated with a copper alloy, which is characterized in that the sintered alloy comprises, as expressed in weight percent, 0.5 to 1.7% C, 0.5 to 2.5% Ni, 3.0 to 8.0% Cr, 0.1 to 0.9% Mo, 1.0 to 3.8% W, and 4.5 to 8.5% Co, the balance being substantially Fe provided by a base atomized powder, and contains 8 to 14% by volume of C--Cr--W--Co--Fe and Fe--Mo hard grains, both having a size of 250 mesh or less; the amount of cells formed using the atomized powder is 6 to 13% by volume, with an amount of closed cells of 0.4 to 1.2% by volume; and continuous ones of the cells are substantially infiltrated with the copper alloy. 
     
     
       2. A sintered alloy material as claimed in claim 1, wherein the sintered alloy comprises 1.0 to 1.5% C, 0.8 to 2.3% Ni, 3.5 to 7.5% Cr, 0.3 to 0.7% Mo, 1.3 to 3.3% W, and 5.0 to 8.0% Co, the balance being substantially Fe, and the cells contain 9.5 to 14.0% Cu. 
     
     
       3. A sintered alloy material as claimed in claim 2, wherein the C--Cr--W--Co--Fe grains comprise, as expressed in weight percent, 2.0 to 3.0% C, 7.0 to 15% Co, 15 to 25% W, and 1.0 to 8.0% Fe, the balance being substantially Cr. 
     
     
       4. A valve seat for an intake/exhaust valve of an internal combustion engine formed of the sintered alloy of claim 1.